1. Field of the Invention
The present invention generally relates to the computation of three-dimensional linkage structures, and more particularly to a method for calculating the deformation of a human spine caused by disease.
2. Background Description
Every year, approximately one-half million operations are performed in the United States on the spine. Many of these operations are performed to treat severe scoliosis, a condition which results in an acute curvature of the spine. Unfortunately, scoliosis and other spinal deformities have proved difficult to treat, and in fact represent one of the greatest challenges in medicine.
The conventional approach for treating severe deformations of the spine is surgery. Generally, surgery is performed to accomplish two goals; the primary goal is to prevent any further deterioration of the spine and the secondary goal is to correct as much as possible the deformation that has already occurred.
The current surgical procedure for correcting spinal deformities is spinal fusion. This procedure involves the permanent joining together of two or more vertebrae and has, at best, proved to be a temporary solution because it does not address the etiology and pathophysiology of the underlying disease. Other drawbacks of spinal fusion are apparent. For example, it is a crude mechanical approach which often leads to subsequent problems, such as permanent loss in the range of mobility. Also, while it has been recognized that the earlier surgery is performed the better the correction achievable, a decision to operate is often made at a point at which it would be better to do nothing if deterioration would cease.
In view of the foregoing considerations, it would be beneficial to have a methodology for predicting the future course of a spinal disease and its affect on curvature, and moreover to employ this methodology as a non-surgical option for assisting doctors in diagnosing and treating patients with spinal deformities.
It is a first objective of the present invention to provide a method for predicting the future course of a spinal disease in terms of its affect on curvature.
It is a second objective of the present invention to employ a method of the aforementioned type as a non-surgical option for assisting doctors in diagnosing and treating patients with spinal deformities.
It is another objective of the present invention to achieve the aforementioned objectives by formulating a mathematical model which gives a probabilistic indication of the progression of a spinal disease as it matures and the resulting affect on the curvature of a patient""s spine, which model may be used by doctors as a tool for determining whether a surgical procedure could in fact achieve any successful results, and if so to indicate what type of procedure would prove most effective in correcting and/or staying the destructive effects of the disease.
It is another object of the invention to provide an interactive process to determine the surgery to be performed to improve spinal shape.
According to the invention, there is provided a modeling method based on a concept called spinal energy which assumes that the spine assumes a shape to minimize spinal energy. Spinal energy depends on parameters called stiffness coefficients. These parameters can be determined from human data which, by hypothesis, are universal for a large class of humans. The method of the invention adapts Newton""s method to the manifold SO(3)n to find a solution of model of the human spine. Where basins of attraction are small in Newton""s method, we introduce homotopy methods to move from known solutions to unknown solutions.
By setting the gradient of the spinal energy to zero, we can again use Newton""s method to solve the inverse problem of finding stiffness coefficients from human data.
A new approach to improving deformed spines uses the modeling method based on spinal energy. This approach preserves maximally the range of motion of the spine. The technique used is vertebraplasty; i.e., adding and/or removing material surgically from various vertebral bodies without fusing or altering soft tissue. An interactive process is used to determine just what is to be added or removed to improve spinal shape.